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Chapter 26 IP Source Guard
MGS3700-12C User’s Guide
273
• They appear only in the ARP Inspection screens and commands, not in the
MAC Address Filter screens and commands.
26.1.2.2 Trusted vs. Untrusted Ports
Every port is either a trusted port or an untrusted port for ARP inspection. This
setting is independent of the trusted/untrusted setting for DHCP snooping. You
can also specify the maximum rate at which the Switch receives ARP packets on
untrusted ports.
The Switch does not discard ARP packets on trusted ports for any reason.
The Switch discards ARP packets on untrusted ports in the following situations:
• The sender’s information in the ARP packet does not match any of the current
bindings.
• The rate at which ARP packets arrive is too high.
26.1.2.3 Syslog
The Switch can send syslog messages to the specified syslog server (Chapter 41
on page 391) when it forwards or discards ARP packets. The Switch can
consolidate log messages and send log messages in batches to make this
mechanism more efficient.
26.1.2.4 Configuring ARP Inspection
Follow these steps to configure ARP inspection on the Switch.
1 Configure DHCP snooping. See Section 26.1.1.4 on page 271.
Note: It is recommended you enable DHCP snooping at least one day before you
enable ARP inspection so that the Switch has enough time to build the binding
table.
2 Enable ARP inspection on each VLAN.
3 Configure trusted and untrusted ports, and specify the maximum number of ARP
packets that each port can receive per second.
26.2 IP Source Guard
Use this screen to look at the current bindings for DHCP snooping and ARP
inspection. Bindings are used by DHCP snooping and ARP inspection to distinguish
between authorized and unauthorized packets in the network. The Switch learns